312 IODINE IODISM 



from the mother-liquors of the Chili nitre mines iodine is 

 also obtained. 



PROPERTIES. Iodine occurs in soft, friable, black or blue- 

 black, rhombic prisms or octahedrons of a metallic lustre. 

 Its specific gravity is 4-95. It has an acrid, disagreeable 

 taste, and a pungent, unpleasant odour, resembling that of 

 chlorine or sea-water. Applied to the skin it produces a 

 brown stain, readily removed by alkalies. At the tempera- 

 ture of the atmosphere it slowly evaporates ; at 237 Fahr. 

 it melts ; at 392 Fahr. it boils, volatilising entirely in violet- 

 coloured, irritating, antiseptic vapours, nine times as heavy 

 as air. With water it forms a brownish-yellow solution, 

 containing, however, only '05 per cent. It is dissolved by 

 twelve parts of rectified spirit, and still more readily by 

 ether, volatile oils, chloroform, carbon disulphide, and also 

 by solution of potassium iodide, and other salts. It readily 

 unites with metals ; the iodides of the alkalies closely 

 resemble iodine in their actions ; the iodides of the heavy 

 metals exhibit chiefly the properties of the base. 



Iodine is easily distinguished by its characteristic odour, 

 by the brown stain it leaves on the fingers, by the violet- 

 coloured vapour it evolves when heated, and by the blue 

 colour it forms with cold solution of starch. This starch 

 test is inapplicable when iodine is in combination, from 

 which, however, it is readily set free by a drop of weak 

 chlorine solution, or of diluted nitric acid. Iodine is liable 

 to intentional adulteration as well as accidental impurities. 



ACTIONS AND USES. Iodine resembles the other halogens, 

 alike in chemical and physiological actions. Its notable 

 affinity for hydrogen, and its combining with albumin, 

 determine its stimulant, irritant, and caustic effects, as well 

 as its antiseptic, alterative, and resolvent actions. It acts 

 notably on mucous membranes, skin, and lymphatic glands. 

 It is almost a specific for diabetes insipidus in horses. Full 

 doses persisted with produce a state of debility and emacia- 

 tion termed iodism. Externally, it is applied as an anti- 

 septic, stimulant, counter-irritant, and parasiticide. It is 

 employed for the several purposes of an antiseptic, deodorant 

 and disinfectant. 



GENERAL ACTIONS. It is an active antiseptic, whether used 



